I recently found MMM and was in similar position as you are now.
I bought a Jeep Wrangler sport in 2012 and traded it in 2013 for a brand new scion FR-S, with negative equity on the top of $25 loan.
Then I moved to CT, where my FR-S which is stick, RWD sat in the garage all winter. I cant take the damn thing out to a gas station when there is < 1 inch of snow. ( buying this car was just one of the numerous worst financial mistakes I made)
I came here and needed that little push, sold my car and had to pay $2k out of my pocket. I didnt SELL it, I got RID of it :)
though I had to pay $2k out of my pocket to pay off the difference between the selling price and loan amount, I dont have to pay $600 every month for a car that rests in garage all winter.
Please make that decision and sell it for loss, if you have to. I am sure, after 1 month, you will have a smile on your face when you dont have a huge monthly car payment.